这个词是什么意思？
An Order of aquatic INSECTS comprising about 2,500 species worldwide. It is the only insect group with two flying stages, each with relatively large forewings. The immature stage called naiad or nymph lasts one year in fresh water, and the adult stage is shortlived, lasting from a few minutes to a few days, depending on the species. The Ephemeroptera includes mayflies (also called shadflies)
中文名称索引；定义为 MeSH 英文原文，尚未逐条译审。MESH:D065133 · MeSH 2026。
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